1. Field of the Invention
The invention is concerned with copper based alloys.
2. Description of the Prior Art
Cu-Ni-Sn alloys have received considerable attention in connection with the manufacture of articles which may be shaped as cast, as hot worked, or as cold worked. For example, E. M. Wise and J. T. Eash, "Strength and Aging Characteristics of the Nickel Bronzes," Trans. AIME, Institute of Metals Division, Vol. 111, pages 218-243 (1934) , and T. E. Kihlgren, "Production and Properties of Age Hardenable Five Percent Nickel-Bronze Castings," Trans. AFA, Vol. 46, pages 41-64, (1938), disclose Cu-Ni-Sn alloys which are strong and hard and which are suitable for certain casting applications. More recently, Cu-Ni-Sn alloys have been developed which are strong and ductile and which are suitable in the manufacture of electrical wire, wire connectors, and springs. Specifically, U.S. Pat. No. 3,937,638, "Method for Treating Copper-Nickel-Tin Alloy Compositions and Products Produced Therefrom," issued to J. T. Plewes on Feb. 10, 1976, discloses articles which are processed by homogenizing, substantial amounts of cold working such as drawing, rolling, or swaging, and aging by an amount which is dependent on the specific amount of cold work used. In contrast to the alloys disclosed by Eash and Wise, these more recently developed alloys exhibit predominantly a spinodal structure and attendant high levels of strength and ductility.
U.S. Pat. No. 4,052,204, "Quaternary Spinodal Copper Alloys," issued to J. T. Plewes on Oct. 4, 1977, discloses copper based spinodal alloys which are processed in a fashion similar to the alloys disclosed in U.S. Pat. No. 3,937,638, but which contain not only Cu, Ni, and Sn but also Fe, Zn, Mn, Zr, Nb, Cr, Al, or Mg in amounts within specified limits. Allowed U.S. application Ser. No. 685,262, filed by J. T. Plewes on May 11, 1976, discloses copper based spinodal alloys having compositions similar to the composition of alloys disclosed in U.S. Pat. Nos. 3,937,638, and 4,052,204, but which are cold rolled by amounts in the range of from 25-45 percent so as to achieve essentially isotropic formability in the rolled product. Resulting strip material is particularly suited for applications which require sharp bending such as in the manufacture of clips and electrical connectors.
U.S. patent application Ser. No. 838,141, filed by J. T. Plewes on Sept. 30, 1977, discloses spinodal Cu-Ni-Sn alloys containing prescribed amounts of Mo, Nb, Ta, V, or Fe and which are suitable for applications in which articles are shaped by hot working such as forging, extruding, or hot pressing or in which articles are shaped as cast.
A specific application of Cu-Ni-Sn alloys which are strong and hard is disclosed, e.g., in U.S. Pat. No. 3,817,487, "Cast Mold of Cu-Sn-Ni Alloy," issued to J. H. Bateman on June 18, 1974, in which their use for molding plastic articles is disclosed. A different application of Cu-Ni-Sn alloys is disclosed in U.S. Pat. No. 4,046,596, "Process for Producing Spectacle Frames Using an Age-Hardenable Nickel-Bronze Alloy," issued to R. T. Metcalfe et al., on Sept. 6, 1977, which discloses the use of such alloys in cold-drawn eyeglass frames.
As evidenced by the above-cited references, Cu-Ni-Sn alloys have proved to be suitable for the manufacture of articles shaped by working or shaped as cast. It has been realized, however, that alloys as disclosed are less suited for shaping by machining such as, e.g., in the manufacture of nuts, bolts, and slotted tubes from rod stock by drilling, lathing, or milling. Among undesirable effects observed during machining of such alloys are clogging of drill bits, overheating of machining tools and workpiece, and the formation of continuous strands of machined material which may get entangled with a rotating machining tool or workpiece.